Refrigerated display cases, often referred to as coolers or freezers, are commonly found in grocery stores, markets, convenience stores, liquor stores and other retail businesses for the preservation and display of food and beverages. Conventional display cases comprise an inner refrigerated space defined by a collection of structural elements or members, and an opening further defined by the structural elements that is accessible by a sliding or swinging door. Typically, the door is formed from a plurality of frame members that support at least one layer of glass and a handle. The collection of structural elements that form the display case include interior and exterior frame members, including “mullions” which are vertical elements that extend between upper and lower frame members, typically in a frontal area of the display case. An end mullion is a peripheral vertical element that is located at one end of the display case, and a center mullion is a central vertical element that is located between two openable doors. The mullion provides an engaging surface for the door seals that are used to maintain the lower temperature within the display case. As such, the mullion is part of a door frame sealing system for the free-standing display case.
Certain retail businesses, such as convenience and liquor stores, include a “walk-in” cooler or room instead of a free-standing refrigerated display case. These walk-in coolers are not free-standing as recognized within the industry, however, they include a number of similar components including mullions and openable doors with seals.
Regardless of whether the refrigerated case is free-standing or walk-in, the door frame members and the door glass conduct ambient heat into the display case and function as a condensation surface for water vapor present in the ambient air. Also, the opening of the doors by consumers to access the food or beverage products within the case increases the heat transfer and condensation formation. To reduce condensation on the door frame and glass, and fogging of the door glass, a heating element or wire may be installed within the door frame and/or mullion to warm the door seals and frame and thereby reduce condensation. In addition, warming of the door seals increases the effectiveness of the seal between the door and the mullion, and increases the integrity and lifetime of the seal. Of course, the operating costs of the case is further increased by the energy consumed by the heating element.
The present invention seeks to overcome certain of these limitations and other drawbacks of the prior art, and to provide new features not heretofore available. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.